Crystalline Derivatives of Dipyrazolo-1,5-diazocine and Dipyrazolopyrimidine: A Case of Unexpected Synthesis and Isostructural Polymorphism

Pyrazole-phenylmethanimines (Shiff bases), Py–N=CH–Ph, form molecular crystals whose supramolecular and self-assembly properties can be tuned according to the substitution made on aromatic pyrazole rings. In pursuit of first pyrazole-pyridinemethanimine member, Py–N=CH–Pyr, by following well-known synthetic scheme for these Shiff bases, two hitherto unknown crystalline derivatives dipyrazolo-1,5-diazocine dipyrazolopyrimidine were obtained instead, this depending use or not acetic acid as catalyst. 1,5-diazocine crystallizes in a single P-1 triclinic packing system (Z = 2, Z′ 1), while exhibits isostructural dimorphic behavior adopting (pale pink yellow) alike P21/c monoclinic systems (both Z 4, 1) function solvent used. Crystal structures resolved means X-ray diffraction technique their intramolecular, intermolecular, assemblies analyzed with assistance decorated Hirshfeld surfaces topology study electron density using quantum-theory atoms molecules (QTAIM). Although both polymorphs are stabilized same type noncovalent motifs, pale crystal has slightly more compact structure, efficient inter- intramolecular interactions.